I had been living in Rome for a few months and read an article in a local magazine about Calcata. It seemed to be just about the most intriguing place I’d ever heard of: a medieval fortress town on four-hundred-and-fifty-foot cliffs inhabited by the artists and hippies (since the nineteen-sixties) who saved the village from demolition. So I went there on a day trip and fell in love with it. It was also on that trip when I heard about another intriguing aspect about Calcata: that for centuries it was home to the Holy Foreskin, and since the nineteen-eighties this bizarre holy relic has been missing. A couple years later, now living in New York, I was ready to start a book project—Calcata and the Holy Foreskin came to mind.

In the span of a few hundred years, the Holy Foreskin went from revered relic to an embarrassment to the Catholic Church. Why?

It’s exemplary of the history of relics—or, rather, of how their function has changed and been quietly de-emphasized within the Church. One of the results of the Second Council of Nicaea, in 787, was a law stating that every church altar had to have a relic inside it. That law was put to rest in the late nineteen-sixties (as an addendum to the Second Vatican Council reforms that took place earlier that decade).

As for the “carne vera sacra,” the real holy flesh, as they called it in Calcata, it fell out of favor with the Church for a few different reasons. Until the middle of the twentieth century, Calcata was an isolated hill town (despite only being thirty miles north of Rome). You had to take a “mule road” to get there. Thus, the relic was venerated but in a very low-key fashion. Then, starting in the middle of the nineteenth century, a French village called Charroux—which had been famous in the Middle Ages for having a supposed Holy Foreskin—announced they’d rediscovered their miraculous membrane hidden in one of the walls inside the abbey. A big deal was made of it and the Protestant press attacked the Church. It didn’t help that yet another French village, which was also linked to a Holy Foreskin in the Middle Ages, announced in the nineteenth century that theirs, too, had been rediscovered. So, I think, Pope Leo XIII, who was staunchly anti-modernity, just wanted to put the whole issue to bed. He eventually made a decree threatening excommunication to anyone who spoke of or wrote about the Holy Foreskin.

The Church’s resistance was just one of several roadblocks in your research—you had to deal with language barriers and easily offended locals, too. Which problem was most difficult for you as a writer?

The Vatican’s reluctance to talk not just about the Holy Foreskin, but about relics in general was difficult. I’d made phone calls, sent faxes, paid visits to Vatican offices. Some Vaticanisti were outright dismissive of me (even if I didn’t mention the relic in question) and others were polite, but no one ever would get back to me. I did, however, get myself into the Vatican Library for a few months and it was a lot of fun digging up centuries-old documents written about Jesus’s foreskin (complete with the papal imprimatur). I ended up getting a lot of crucial information from Church insiders or others who knew people within the Church.

Why did you write the book as a first-person detective story, rather than a straight history of the relic?

When the relic disappeared in the nineteen-eighties, the villagers were left with several intriguing theories about what happened to it—that neo-Nazis or Satanists stole it, that the priest sold it, and even that the Vatican itself had something to do with it. Part of my motivation for writing the book was to figure out what really happened to it. But besides that, I wanted to capture a sense of Calcata as well. It’s one of the most unusual places in Italy, and I thought my interactions with the locals would add a different dimension to the narrative.

The book mentions other weird relics, including the breast of Mary Magdalene and the head of St. John—as a baby. Is there a sequel in the works?

In terms of related subjects, the Holy Foreskin is a hard act to follow. I’m already working on another book project, but it’s not related to religion or holy genitalia or even Italy. Which is a good thing, because I’m not sure the Vatican would let me back in.